Extract stream management into `ppm_pixel_stream`, provide Cartesian coordinates

2 files changed, 50 insertions, 20 deletions

diff --git a/src/imgen.cc b/src/imgen.cc
index d574672..25731e1 100644
--- a/src/imgen.cc
+++ b/src/imgen.cc
@@ -1,34 +1,50 @@
 #include "imgen.h"
 
-#include <fstream>
-
 namespace {
 
 inline void write_color(std::ofstream& out, const imgen::color& color) {
-	out << std::get<0>(color);
-	out << std::get<1>(color);
-	out << std::get<2>(color);
+	out << std::get<0>(color)
+	    << std::get<1>(color)
+	    << std::get<2>(color);
 }
 
 }
 
 namespace imgen {
 
+ppm_pixel_stream::ppm_pixel_stream(
+	const std::string& path,
+	const std::size_t  width,
+	const std::size_t  height
+): stream_() {
+	this->stream_.open(path, std::ios::binary | std::ios::out);
+	this->stream_.sync_with_stdio(false);
+
+	this->stream_ << "P6\n" << width << " " << height << "\n255\n";
+}
+
+ppm_pixel_stream& ppm_pixel_stream::operator<<(const color& value) {
+	write_color(this->stream_, value);
+
+	return *this;
+}
+
 void write_ppm(
-	const std::string&                             path,
-	const std::size_t                              sizeX,
-	const std::size_t                              sizeY,
-	std::function<color(std::size_t, std::size_t)> generator
+	const std::string&                                   path,
+	const std::size_t                                    width,
+	const std::size_t                                    height,
+	std::function<color(std::ptrdiff_t, std::ptrdiff_t)> generator
 ) {
-	std::ofstream out;
-	out.open(path, std::ios::binary | std::ios::out);
-	out.sync_with_stdio(false);
+	ppm_pixel_stream file(path, width, height);
 
-	out << "P6\n" << sizeX << " " << sizeY << "\n255\n";
+	const std::ptrdiff_t min_y = height / 2 * -1;
+	const std::ptrdiff_t max_y = height / 2;
+	const std::ptrdiff_t min_x = width  / 2 * -1;
+	const std::ptrdiff_t max_x = width  / 2;
 
-	for ( std::size_t posY = 0; posY < sizeY; ++posY ) {
-		for ( std::size_t posX = 0; posX < sizeX; ++posX ) {
-			write_color(out, generator(posX, posY));
+	for ( std::ptrdiff_t posY = min_y; posY < max_y; ++posY ) {
+		for ( std::ptrdiff_t posX = min_x; posX < max_x; ++posX ) {
+			file << generator(posX, posY);
 		}
 	}
 }
diff --git a/src/imgen.h b/src/imgen.h
index 5ddbaf6..35b798d 100644
--- a/src/imgen.h
+++ b/src/imgen.h
@@ -1,16 +1,30 @@
 #include <string>
 #include <utility>
+#include <fstream>
 #include <functional>
 
 namespace imgen {
 
 using color = std::tuple<std::uint8_t, std::uint8_t, std::uint8_t>;
 
+class ppm_pixel_stream {
+	public:
+		ppm_pixel_stream(const std::string& path,
+		                 const std::size_t  width,
+		                 const std::size_t  height);
+
+		ppm_pixel_stream& operator<<(const color& value);
+
+	private:
+		std::ofstream stream_;
+
+};
+
 void write_ppm(
-	const std::string&                             path,
-	const std::size_t                              sizeX,
-	const std::size_t                              sizeY,
-	std::function<color(std::size_t, std::size_t)> generator
+	const std::string&                                   path,
+	const std::size_t                                    sizeX,
+	const std::size_t                                    sizeY,
+	std::function<color(std::ptrdiff_t, std::ptrdiff_t)> generator
 );
 
 }